Charles Spurgeon Commentary Ecclesiastes 11:8-9

"Yea, if a man live many years, let him rejoice in them all; but let him remember the days of darkness, for they shall be many. All that cometh is vanity. Rejoice, O young man, in thy youth, and let thy heart cheer thee in the days of thy youth, and walk in the ways of thy heart, and in the sight of thine eyes; but know thou, that for all these things God will bring thee into judgment." — Ecclesiastes 11:8-9 (ASV)

But if a man live many years, and rejoice in them all; yet let him remember the days of darkness; for they shall be many. All that cometh is vanity. Rejoice, O young man, in thy youth; and let thy heart cheer thee in the days of thy youth, and walk in the ways of thine heart, and in the sight of thine eyes: but know thou, that for all these things God will bring thee into judgment.

Nobody sensible supposes that Solomon exhorted young men to walk according to their own heart and according to the sight of their eyes.

This is a common way of speaking; for instance, we might say to a man who is going to excess in drink, "Well, drink your fill, and get drunk; but you will have to suffer for it. It will certainly exact a penalty from you eventually." Nobody would be so foolish as to say that we had exhorted the man to drunkenness.

On the contrary, we did, in effect, warn him not to continue in his evil course by reminding him of the penalty that would assuredly follow. So, here, Solomon seems to say, "Do this if you will; do it if you dare; but remember that there is a judgment day coming, and that God will judge you for all these things, and according to these things He will measure out your doom."